Don’t let this happen to your permit-required confined space entrant
OSHA reported this permit space accident that killed a construction foreman. The foreman had 15 years of experience and died from asphyxiation after entering a manhole with an uncontrolled hazardous atmosphere.
It happened like this
Four construction workers were working in an inactive sewer system on a jobsite that was unoccupied for over a week. A few minutes after they started working, the crew noticed that the foreman was missing, and a manhole cover was removed. While one worker called emergency services, a second worker entered the manhole to assist the foreman and found him unresponsive at the bottom of the 20-foot manhole.
When the second worker became disoriented inside the manhole, another worker used a fan to blow fresh air into the manhole and the worker was able to climb out. The foreman was retrieved by fire department personnel and was later pronounced dead due to asphyxiation.
Likely causes of the incident
The manhole was newly constructed and not yet connected to an active sewer system at the time of this incident. However, it contained a hazardous atmosphere that resulted in asphyxiation.
The failures were many, including:
- The employer didn’t have a permit space program in place, per 1910.146(d).
- The employer didn’t ensure that atmospheric hazards were identified and precautions for safe operations implemented before starting work at the site.
- Workers weren’t trained to recognize confined space hazards and to take appropriate protective measures.
- The atmosphere in the manhole wasn’t assessed to determine if conditions were acceptable before or during entry.
- Proper ventilation wasn’t used to control atmospheric hazards in the manhole.
- Protective and emergency equipment wasn’t provided at the worksite.
- An attendant wasn’t stationed outside the manhole to monitor the situation and call for emergency services.
Cause of death
Asphyxia occurred when the foreman did not get enough oxygen tosustain life, either because the amount of oxygen in the atmosphere was too low (i.e., oxygen deficiency) and/or a hazardous chemical concentration was too high (e.g., high carbon dioxide level).
Although the exact atmospheric conditions in the manhole at the time of the incident are unknown, measurements taken after the incident indicate it was possible the oxygen levels were low enough and/or carbon dioxide levels were high enough to cause asphyxiation.
The investigation revealed interesting facts
When rescuers arrived, the atmosphere contained 19.1% oxygen, however, this measurement was taken after construction workers had used a fan to provide fresh air to the disoriented worker. One day after the incident, the atmosphere contained 16.5 percent oxygen and four days after the incident the oxygen concentration dropped to 7.7 percent.
Hazardous atmospheres in OSHA’s Confined Spaces in Construction standard include atmospheres with less than 19.5 percent oxygen (29 CFR 1926.1202). Normal atmospheric oxygen level is between 20.8 percent and 21 percent. Four days after the incident, the carbon dioxide concentration was 6.5 percent. An atmosphere with 4 percent or more carbon dioxide is considered Immediately Dangerous to Life or Health according to the National Institute for Occupational Safety and Health.
Changes in atmospheric conditions over time might be due to several causes. For example, organic matter (e.g., dead plants, animals, or animal waste products) decay in soil that uses up oxygen and produces hazardous gases (e.g., carbon dioxide, hydrogen sulfide). Although conditions within these spaces could seem acceptable during initial entry, atmospheric changes could occur over time and result in fatalities.
Key to remember
Because permit spaces are extremely dangerous environments, everyone involved must understand their employer’s permit space program for controlling and protecting employees from permit space hazards.